Conventionally, electrical contacts for axial nanowire devices are made by encapsulating the nanowires in an insulator and then etching the insulator to expose the tops of each wire. A conducting material is then deposited to make the electrical contacts to the nanowires.
The present inventors observed that 1×1 mm2 prior art InP nanowire solar cells have an average open circuit voltage, Voc, which is significantly lower (500-700 mV) than what would be expected from an ideal InP solar cell (900 mV). In addition to the lower average Voc of the nanowire solar cells, the spread in Voc is typically large, with a standard deviation of several 100 mV. Thus, nanowire solar cells with a higher open circuit voltage and a small spread in open circuit voltage are desired.